(1) Field of the Invention
The present invention relates to an optical data recording/reproduction apparatus which incorporates an optical pickup for recording or reproducing a data signal on an optical data recording medium.
(2) Description of the Related Art
Generally, when an optical data recording medium is tilted, coma aberration occurs and the focused light spot on the data recording surface of the data recording medium deteriorates, so it becomes impossible to record and/or reproduce data signals normally. Such coma aberration is proportional to the cube of the objective lens numerical aperture (NA) and proportional to the reciprocal of the laser wavelength. For BDs (Blu-ray Disc) in particular, the objective lens NA is 0.85 which is larger than that for DVDs, and the laser wavelength is as small as 405 nm. Therefore, for BDs, it is important to reduce coma aberration.
As an example of a solution to this problem, JP-A No. 2010-140566 discloses a technique which reduces coma aberration properly when the ambient temperature changes. It describes that for the objective lens, (1) a lens tilt correction is made if the lens tilt sensitivity is a prescribed value or more, and (2) a lens tilt correction is not made if the lens tilt sensitivity is less than the prescribed value.